IA. Field of the Invention
This invention relates to quality of service (QoS) for network communication. Specifically a new form of QoS, called soft-QoS, is introduced to bridge the gap currently existing between the efficient provision of network-level QoS and the requirements of multimedia applications. This invention is embodied in a network system that uses soft-QoS, in a method for utilizing soft-QoS and a computer program product that enables a network to use soft-QoS.
IB. Related Work
Presently, communication over a network has become widely prevalent. Connections that use such a network require a guarantee of a certain quality of service. Quality of service (QoS) offered by a network connection is measured in terms of QoS parameters. QoS parameters, in conventional systems is expressed in statistical terms such as cell loss rate, delay jitter and cell transfer delay.
In order to provide guarantee of a certain QoS, a network needs to make long-term assumptions on the statistical characteristics of its traffic. But then, network traffic is comprised of various connections with their own respective characteristics. Additionally, assumptions made by a network regarding a specific connection must be valid for its entire duration. Above mentioned, statistical characteristics are obtained in conventional systems using methods including stochastic modeling or statistical analysis of empirical data.
But then, traffic profiles of an interactive multimedia connections is generally unknown when it is setup. Therefore, above mentioned long-term statistical representations are unsuitable for such interactive multimedia connections. Specifically, parameters used in long-term statistical representations do not represent the specific QoS requirements of multimedia applications. It is generally accepted that distributed multimedia applications require a network service that can match the dynamic and heterogeneous bandwidth requirements that are typical of such applications.
FIG. 1 shows an example of how video bit-rate significantly changes over a session. On the x-axis frames corresponding to the video data are represented. Size of the data in terms of number of bits are represented in the y-axis. FIG. 2 shows frame rate from a source and a compounded multimedia traffic on a network.
Moreover, a network has to rely on conservative traffic assumptions to guarantee a certain QoS. Such reliance on conservative assumptions lead to reservation of network capacity far in excess of what is required. Consequently, there is poor network utilization.
It should be noted that problem of poor network utilization due to capacity over-reservation has been addressed by practitioners in this field using VBR+. See D. Reininger, G. Ramamurthy and D. Raychaudhuri, xe2x80x9cVBR MPEG Video Coding with Dynamic Bandwidth Renegotiation,xe2x80x9d Proceedings of ICC (June 1995). VBR+ is a network service class, using which a connection can renegotiate its bandwidth while the connection is in progress.
Using this methodology overall utilization of a network is improved since bandwidth can be dynamically allocated and reallocated during a connection. See D. Reininger, W. Luo, xe2x80x9cStatistical Multiplexing of VBR+ video,xe2x80x9d Proceedings of SPIE International Symposium on Voice, Video and Data Communications, Dallas, Tex. (November 1997).
But then, formulae used in connection bandwidth calculation involve QoS parameters like equivalent bandwidth. Consequently reallocating bandwidth changes the QoS of a connection. In such a case, procedures used for bandwidth reallocation, as in VBR+, have to ensure that new QoS parameters satisfy the original QoS requirements of a connection. In order to realize this objective, the authors use a concept of xe2x80x9cQoS satisfactionxe2x80x9d.
Methods known conventionally are based on representing QoS satisfaction as a xe2x80x9chardxe2x80x9d binary (xe2x80x9cyes/noxe2x80x9d) parameter. If, for example, the delivered (or estimated) cell loss ratio is larger than a required cell loss ratio, the connection is deemed unsatisfied. This result is notwithstanding however small the discrepancy between the required and delivered cell loss ratio is.
Taking the above into consideration, it is thus clear that using binary parameters lead to an overgeneralization of QoS satisfaction. This has been partially rectified in conventional systems by using two sets of QoS parameters at the setup phase, they being desired QoS and acceptable QoS.
A user connection and a network engage in a sequence of QoS negotiations using the above mentioned two parameters. In such a case, the user connection is assigned acceptable QoS parameters which may be different from the desired QoS originally requested by it. Although this methodology presents an improvement over the earlier mentioned binary characterization of QoS satisfaction, providing a desired and acceptable QoS does not lead to an adequate mechanism to handle QoS that fall between the two. It is amply clear that the region between the QoS boundaries, desired and acceptable, is not used effectively.
Also, conventional systems do not have a QoS satisfaction scheme that can be employed while a connection is in progress. Besides, it is not possible for a network to achieve high utilization while maintaining hard-bound long-term QoS guarantees under the requirements imposed by distributed multimedia-applications.
Therefore, at least the following problems exist in conventional network systems.
xe2x80x9chardxe2x80x9d QoS is inadequate for multimedia traffic.
xe2x80x9chardxe2x80x9d QoS leads to unsatisfactory utilization of networks.
Conventional QoS satisfaction schemes can not be modified while a connection is in process.
Conventional QoS satisfaction schemes do not provide quality-fair resource allocation since they use equal bandwidth allocation.
It is an objective of this invention to solve the above identified problems in network systems. Specifically, it is an objective of this invention to provide a soft-QoS for balancing network utilization and application-level QoS in distributed multimedia systems.
It is another objective of this invention to use during congestion a soft-QoS for utilizing the tolerance of an application to network bandwidth shortage. It is an objective of the present invention to represent soft-QoS by a satisfaction index and a softness profile.
In case of video transmission, satisfaction index is an indication of perceptual quality. For different multimedia applications, softness profile correlates the satisfaction index to the resulting bandwidth allocation during network congestion. For example, video applications exhibit a non-linear quality response to bit-rate changes. Scaling a video source reduces its bit-rate, but impacts the perceptual quality. While xe2x80x9csoftxe2x80x9d applications (such as teleconferencing or multimedia-on-demand browsing) can tolerate relatively large reductions in bit-rate, xe2x80x9chardxe2x80x9d applications (such as video on-demand or medical applications) cannot tolerate bit-rate scaling without significantly degrading the application-level QoS. Softer applications are more robust to network congestion since they exhibit a slower decay in satisfaction index with increasing bandwidth shortage.
It is yet another objective of the present invention to use softness profiles of various applications in a network to balance bandwidth utilization and user satisfactions. It is yet another objective of this invention to enable softer applications to receive a favorably priced service for their added flexibility to the bandwidth allocation allowing networks to operate at more aggressive utilization regimes.
It is another objective of this invention to address the issues relating to QoS and expand the notion of QoS satisfaction beyond its current xe2x80x9chardxe2x80x9d binary status.
Specifically satisfaction index is gradually scaled from xe2x80x9cunsatisfiedxe2x80x9d to xe2x80x9csatisfied. Satisfaction index represents the discrepancy, between the requested equivalent bandwidth and the allocated bandwidth during a network congestion. The exact relationship between the satisfaction index and the bandwidth of the connection is described by its softness profile. Softness profile specifies how satisfaction index decreases if only a portion of the requested bandwidth can be actually allocated by the network. If a small bandwidth deficit causes sharp decrease of the satisfaction index, the corresponding softness profile is deemed xe2x80x9chardxe2x80x9d. xe2x80x9cSofterxe2x80x9d profiles correspond to cases, where bandwidth deficit cause the satisfaction index to decrease slower. Softness profile can be selected during setup and it can be changed while a session is in progress.
It is yet another objective of this invention to enable applications to choose a softness profile that best suits their needs. For example, video-on-demand (VoD) applications generally tolerate bit-rate regulations within a small dynamic range, (since rate control is achieved through quantizer control). Applications such as surveillance or teleconference may have a larger dynamic range for bit-rate control since video can be displayed over a range of frame-rates below the traditional 30 and 24 frames-per-second. Other multimedia applications may allow a larger range of bit-rate control by resolution scaling. In these examples, VoD applications are matched to a xe2x80x9charderxe2x80x9d profile than the other, more adaptive multimedia applications.
It is yet another objective of the present invention to enable applications to choose appropriate softness profiles depending on the nature of the application. For example, users on wireless mobile terminals may select a xe2x80x9csofterxe2x80x9d profile for an application in order to reduce the connection""s cost, while a xe2x80x9charderxe2x80x9d profile may be selected when the same application is run on a wired desktop terminal. Thus, adaptive multi-media applications able to scale their video quality could specify their soft-QoS requirements dynamically to control the cost of a session.
In order to achieve the objectives noted above it is provided a distributed multimedia system having a soft quality of service support. Additionally it is provided a distributed multimedia system comprising a client, a server and a network, wherein the client further comprises an application and a network interface card, the server further comprises a terminal quality of service controller, a data source and a server network interface card.
In a preferred embodiment the network further comprises a backbone network, an access network, quality of service controller, the quality of service controller attached to the access network.
Further preferred embodiments include improvements where the service controllers can be personal computers, function servers and embedded systems.
Further preferred embodiments include improvements where the service controllers reside in the edge switch of the backbone network and/or be distributed across the backbone network.
Another aspect of the present invention is a soft-QoS having a softness profile and a satisfaction index. Improvements include a softness profile defined using a satisfaction index and bandwidth ratio, the bandwidth ratio being further defined as a ratio of allocated bandwidth to requested bandwidth, satisfaction index is graded from 2-5 with a granurality of G and said bandwidth ratio is graded from 0-1. Further improvements include mathematical formulations to calculate softness profile which are subsequently described with reference to preferred embodiments.
In yet another preferred embodiment an application can request bandwidth from a network in terms of soft quality of service while connection is in progress, the application can also renegotiate soft quality of service requirements, and the quality of service controllers compute and negotiate bit-rates necessary to maintain quality. Improvements include a preferred embodiment where the renegotiation is invoked by the network or the user. A network may invoke renegotiations to ensure quality-fairness among competing connections. The renegotiation is sent to network switches in yet another preferred embodiment.
Preferred embodiments include a system where the data source is a multimedia bit-rate source and the multimedia data source such as a video data source uses frame rate and frame detail as soft-QoS parameters.
Another aspect of the present invention is a method of processing quality of service renegotiation by a soft quality of service controller comprising receiving a bandwidth request, receiving softness profile associated with the bandwidth request, granting the request if a decrease is requested and granting a request for increase if capacity is available. In a preferred embodiment a request for bandwidth increase is granted by making a preliminary allocation at output port, computing a satisfaction index, using a reallocation algorithm to reclaim additional bandwidth if said satisfaction index is low.
Another aspect of this invention is a reallocating method for reallocating bandwidth in a network, the network comprising donor connections and recipient connections, the recipient connections and the donor connections being associated with a satisfaction profile each, wherein each of the satisfaction profiles maximizes a minimum satisfaction index so that the satisfaction index is within an acceptable range.
Another aspect of the present invention is a reallocation method to reallocate bandwidth among a plurality of donor connection and a recipient connection comprising identifying donor connections with higher satisfaction index, identifying donor connections with higher allocated bandwidth, calculating amount of bandwidth that would be reallocated using softness profiles, wherein an amount of released bandwidth is selected such that the remaining bandwidth reduces said satisfaction index by a unit of granurality G, stopping when satisfaction index of the recipient connection is within a threshold, repeating the above steps until the satisfaction index of the recipient connection is in an acceptable region or satisfaction index of any connection other than the recipient reaches minimum satisfaction and requesting for more bandwidth from network layer if minimum satisfaction is reached.
In a preferred embodiment the donor connections are identified using a method comprising determining a pruning threshold and including a connection in a list of donor connections if the pruning threshold times current allocation bandwidth is larger than the bandwidth required.
Another aspect of the present invention is a method of calculating softness profile by approximation with a piecewise linear function wherein the function correlates satisfaction index and bandwidth ratio, wherein said function consists of a plurality of linear segments, the slope of each linear segment represents a rate at which video quality degrades because of shortages in the allocated bandwidth.
Another aspect of the present invention is a method of calculating bandwidth required to obtain a satisfaction indexes using a formula described in detail subsequently with respect to preferred embodiments.
Yet another aspect of the present invention is a method of admittance control wherein an average low satisfaction rate is less than the maximum low satisfaction rate, wherein the average low satisfaction rate is equal to a probability that long term capacity requirement of the connection is greater than a listed bandwidth.
Another aspect of this invention is a method of admittance control in a network system comprising advertising a reference profile, converting the reference profile into soft-UPC parameters, deriving a two state traffic model using said soft-UPC parameters and adjusting mean and standard derivation of the bandwidth.
In a preferred embodiment adjusting mean and standard deviation comprises determining whether the request is a call arrival or call departure, performing call procedures accordingly. Preferred embodiments include specific methods to perform call arrival and call departure procedures. Yet another preferred embodiment includes parameters to use for advertising during the call set up phase. Yet another preferred embodiment includes mathematical formulae for each of the steps in admittance control which are described in detail subsequently with reference to preferred embodiments.